Enhancing Mechanical, <scp>EMI</scp> Shielding, and Thermal Properties of Pitch‐Based Carbon Fiber Composites via <scp>MXene</scp> /Polydopamine Modification

ABSTRACT Mesophase pitch‐based carbon fibers (PCF) are appealing for high‐performance multifunctional composites due to their remarkable elastic modulus and axial electrical and thermal conductivity. However, their inert surfaces result in poor interfacial adhesion with polymer matrices, limiting their full application potential. This work demonstrates a surface modification method using Ti 3 C 2 T x MXene and polydopamine (PDA) to improve the interfacial adhesion and multifunctional potential of PCF/epoxy composites. The MXene/PDA was coated onto PCF using a simple aqueous self‐polymerization technique. PDA acts as a bridge to connect MXene and PCF, while MXene imparts functional properties to PCF. X‐ray photoelectron spectroscopy validated the effective increase in functional groups, and surface analysis demonstrated a considerable increase in surface roughness and surface free energy of PCF. The modified composites performed much better in interfacial properties, with a 51.41% increase in transverse fiber bundle strength and a 55.17% rise in interlaminar shear strength. Furthermore, the electromagnetic interference shielding effectiveness in the X‐band increased from 20.7 dB to 34.8 dB. Concurrently, the through‐thickness thermal conductivity of the composites increased by 36.4%. These findings indicate that interface modification presents a versatile approach to simultaneously enhance the mechanical, electromagnetic shielding, and thermal conductivity performance of PCF‐reinforced epoxy composites, suggesting its potential application in electromagnetic protection and heat dissipation systems for aerospace and electronic equipment.